Multiplexed Protein Detection Using Magnetic Nanotags

Sensitive and multiplex detection of oncoproteins is vital to the biomedical community as an alternative method to diagnose cancer in whole blood. Conventional assays such as enzyme-linked immunosorbent assays (ELISA) offer high specificity but lack sensitivity and multiplexity. Antigen detection in background of whole blood also poses great challenges optically because of potential interfernce from red blood cells. We have utilized a novel multiplex platform that employs magnetic nanotags to detect antigens/proteins down to subpicomolar concentration level. Unlike fluorescence labels, magnetic nanotags can be detected with inexpensive giant magnetoresistors (GMRs) such as spin-valves without blood  cells interference. As a proof-of-concept, in a reconstruction assay, antigen is added to the antibodies-immobolized sensor array prior to the addition of biotinylated detection antibodies similar to sandwich ELISA. Upon the addition of streptavidin labeled magnetic nanotags, each sensor responds with unique change in magnetic signal. Preliminary results confirm the proof-of-concept with the detection of multiple different antigens/proteins in buffer. In the next phase of the project, the concept will be applied to cancer biomarkers in whole blood.